Process of making a polyester



Patented Feb. 21, 1950 PROCESS OF MAKING A POLYESTER David W. Young,Roselle, and Julius P. Rocca,

Linden, N. J assignors to Standard Oil Development Company, acorporation of Delaware No Drawing. Application April 6, 1945, SerialNo. 587,022

1 Claim.

This invention relates to a novel chemical process and to the productthereof, and to special uses of said product. More particularly, itrelates to a novel chemical reaction, which may be classed as an esterinterchange, particularly with the aid of a special catalyst, with theresulting formation of high molecular weight linear polyesters ofimproved characteristics, including good oil-solubility in hydrocarbonoils, even in paraffinic lubricating oils, in which many prior artpolyesters of high molecular weight have insufficient solubility forcertain desired purposes.

The general chemical reaction of the type in question is already known,i. e., that raw materials containing large amounts of dicarboxylicacids, such as dimerized fatty acids, can be reacted with a glycol tomake high molecular weight polyesters. Howevenmost of such polyesterproducts have been substantially insoluble in paraifinic lubricatingoils at ordinary atmospheric temperatures, and therefore are not suitedfor use as additives for such oils.

One object of the present invention is to make polyesters of highsolubility in parafilnic lubricating oils and to make such polyesters,when added to such oils, have superior properties of improving theviscosity index thereof and also lowering or depressing the pour pointthereof, so that the resultin lubricating oil solutions will pour orflow freely at very cold temperatures and yet will not thin outexcessively at the elevated temperatures generally encountered in use asautomobile or airplane engine crankcase lubricants.

Broadly, the invention comprises reacting a substantially pure dimerizedfatty acid or lower alkyl ester thereof with a glycol in the presence ofa soluble metal soap catalyst. The invention may be illustrated byreacting a purified methyl dilinoleate with decamethylene glycol in thepresence of a small amount of zinc stearate catalyst at elevatedtemperature.

The dimer acid raw material should contain by polymerization ofunsaturated monocarboxylic fatty acids, or lower alkyl esters thereof,such as methyl, ethyl, isopropyl and the like, the methyl esters beingpreferred. This fatty acid raw material may consist of dimerized singlefatty acids or the product resulting from dimerization of a mixture ofmonocarboxylic acids, such as mixed dehydrated castor oil acids, mixedsoybean oil acids and the like. By the term fatty acids, it is intendedto include essentially only fatty acids containing more than 10 carbonatoms and preferably more than 14 carbon atoms before dimerization.

Soybean oil may be converted by methanolysis to methyl esters of thesoybean oil acids by heating to 70 C. with a liberal excess of methanolin the presence of a substantial proportion of sodium methylate forseveral hours, distilling oil! the methyl esters and polymerizing themby heating to 300 C. with a suitable catalyst such as 0.3% ofanthraquinone for a suitable period such as about 10 to 30 hours. Theresultant product comprises essentially methyl dilinoleate esters, witha small amount of trimer esters or other high boiling products, togetherwith some unpolymerized esters which may be removed by distillationunder reduced pressure, e. g., 1 to 5 mm. The relatively pure methyldilinoleate, i. e., the dimer fraction, may be separated from the higherboiling products by any suitable manner such as by careful fractionationin a short path pot still (a modified alembic flask) at about 2 tomicrons, or in a cyclic molecular still at 2 to 5 microns. Substantiallypure methyl dilinoleate made in this manner from soybean oil had anindex of refraction of ND" 1.4766.

The glycol to be used according to this invention may be one having from2 to about or so carbon atoms, but preferably has from 5 to 30 carbonatoms, a still more preferred range being from about 8 to 20 carbonatoms, such as in decamethylene glycol, octadecanediol, 12hydroxystearol, etc. Other examples of glycols that may be used includeethylene glycol, propylene glycol, pentadiol, 2-methy1 2,4-pentadiol, ormuch higher molecular weight glycols such as a dimerized andhydrogenated linoleic acid or other fatty acid. The proportions in whichthe dimer fatty acid, or -ester, and the glycol should be reacted, mayvary somewhat, but should generally be about equimolecular proportionsor, specifically, in the case of methyl dilinoleate and deeamethyleneglycol, the proportion should be about 3 to 1 by weight.

The catalyst to be used is preferably a zinc soap of a higher fatty acidhaving from about 10 to 30 carbon atoms, e. g., stearic acid, palmiticacid, etc., which soap is preferably soluble in petroleum naphtha andother such solvents. Other zinc salts and soaps may be used such as zincnaphthenate, the zinc soap of dilinoleic acid, preferably made from atrimer-free methyldilinoleate, the resulting zinc dimerate preferablyhaving a molecular weight about 1,000. Other metal salts may be used,such as aluminum naphthenate.

Organic salts of polyvalent metals of groups II and III of the Mendeleefperiodic table are preferred. The amount of catalyst to be used mayvary, chiefly according to the temperature of reaction and the strengthof the catalyst, but norm-ally will range from about 0.1% to 3.0% of thetotal weight of reactants, and preferably about 0.3% to 1.0%. The zincdimerate is prepared from potassium dimerate which in turn is preparedby dissolving the dimerized acids in aqueous potassium hydroxide andtreated with zinc chloride to form the zinc dimerate.

The above described reaction or ester interchange may be carried out inthe presence of a solvent or diluent if desired, as for instance in thepresence of 1 to volumes of a hydrocarbon oil such as a minerallubricating oil base stock or a refined kerosene or naphtha, etc. pervolume of mixed reactants.

The polyesterification reaction may be carried out at a suitablyelevated temperature such as about 150 to 250 C., preferably about 180to 220 C.

The reaction mixture is preferably blown with an inert gas such asnitrogen in order to assist in carrying off the water formed by thereaction.

The resulting product is a linear type polyester, of relatively highmolecular weight, such as above 2,000, e. g., 5,000, 10,000, 20,000 andhigher, which is soluble in hydrocarbon oils, even in paraffiniclubricating oil base stocks. This product, which generally is actually amixture of a number of different polyester molecules of slightlydifferent molecular weight may be fractionated if desired, by dissolvingin a suitable solvent, such as a petroleum naphtha or lubricating oilbase stock, and precipitating out one or more fractions by adding asmall amount of non-solvent, such as a low molecular weight alcohol oracetone, etc. This polyester product is substantially free fromcross-linked molecules.

The objects, advantages and details of the invention will be betterunderstood from a'consideration of the following specific examples whichare given merely for the sake of illustration.

Example 1 A mixture of 37 gms. of 100% pure methyl ester of dilinoleicacid and 11.23 gms. of decamethylene glycol was heated with 0.5% of zincdilinoleate at about 192 C. under nitrogen in a Flory viscometer for 5/2 hours. A stream of nitrogen passed continuously through theviscometer served to stir the mixture and to facilitate removal ofalcohols formed in the reaction. No air or oxygen was present in thereaction vessel at any time. The polyester product was recovered bypouring from viscometer while hot. It can also be taken up with solvent,such as a mineral oil, and filtered at room temperature to remove anyinsoluble catalyst.

The final product had a molecular weight of 5,350, based on viscositytests. This condensation product is readily soluble in both paraflinicand naphthenic type lubricating oils, and exhibits thickening andviscosity index improving effects, as shown by the results listed in thefollowing table:

Percent V1sc.at Visc. a gg g fiff, 100r. 210 F.

0 158.25" 44.66 115.9 1 176; 2 4c. 53 121. 0 3 214. s 50. 86 130. 0 s295.3 59.28 134.8

A paraflinic lubricating oil base stock obtained from a Berosa crude. Aparallinic type lubricating oil base stock having a viscosity at 210 F.of 43 S. U. S. and a viscosity index of 112.

The above results indicate that small additions of the polyester raisedthe V. I. of the lubricating oil base stock from about up to 121, and134.8 respectively in concentrations of 1, 3 and 6%. For comparison, asimilar experiment was made in which para toluene sulfonic acid was usedas catalyst in place of the zinc stearate,

Example 2 The first experiment reported above under Example 1 wasrepeated, except that the reaction was carried out for a longer time,namely 12 0 hours, with the resulting formation of a polyester producthaving a molecular weight of about 6,550, which was only required in2.8% concentration in Base Oil A lubricating oil to raise the viscosityto 51 seconds Saybolt universal at 210 F., thereby making a blend havinga V. I. (viscosity index) of 132.

Example 3 Percent pqlymer ss filggisre. at sslzllggiie. at I in oil 7Example 4 Example 3 was repeated except that the ester interchangereaction was carried on for 62 hours total reaction time with the resultthat the polymer formed had the following characteristics:

Percent SSU V150. at SSU Visc. at Polymer V. I.

in on 100 F. 210 F.

Example Percent Polymer SSE??? at 88511851? at I.

Example 6 Example 3 was repeated except that the reaction time wascarried to a total of 140 hours with the resulting formation of apolyester having an average molecular weight of about 9400 which wassubstantially insoluble in the same parafi'lnic lubricating oil basestock used in Example 1. Nevertheless, this high molecular weightpolyester was quite soluble in a naphthenic base oil, and when dissolvedin 15% concentration in such a naphthenic oil of SAE 20 grade, theresulting concentration was found to be soluble in parafliniclubricating oils such as the one used in Example 1. Blends were maderanging from 5 to 20% of this concentrate in a paraflinic lubricatingoil base stock to which had been added 2.5% of a parafiinic Bright Stock(to make a more severe test of pour depressing characteristics), and theresulting blends showed the following pour point and viscositycharacteristics:

Per cent of V15 V15 Polyester Pour V. I. Concentrate The above dataindicate that this polyester had both V. I. improving properties andpour depressing properties when blended into a paraffinic lubricatingoil base stock by means of a small amount of naphthenic oil serving as ablending agent or mutual solvent.

Example 7 Another sample of the same polyester made in Example 6 wasdissolved in 39% by weight concentration in a naphthenic base lube oilof SAE grade 20 and the resultant concentrate was blended into aparaffinic lubricating oil base stock similar to that used in Example 6,except that it contained 3.5% of Bright Stock instead of only 2.5%, theamount of the polyester concentrate added being sufficient to make a 2%final concentration of the polyester in the finished blend, and thenthis blend which had an ASTM pour point of 30 F. (compared to +30 F. forthe paraflinic oil base stock) was subjected to winter field pour pointtests throughout the period from November to January in two coldgeographical locations in the U. 8., namely at Minneapolis, Minn, andWarren, Pa. The sample of oil was observed each morning to see whetherit was solid or would pour. In none of the observations (46 atMinneapolis and 27 at Warren, Pa.) were the blends containing thepolyester of this invention found to be solid, whereas correspondingblends of commercially available pour depressors dissolved in the sameparaflinic oil base stock were found to be solid from 7 to 12 times atMin neapolis and from 2 to 9 times at Warren, Pa., the highest solidpoint being +20 F. at both locations.

Example 8 2 methyl 2 nitro-1,3-propanediol ..gm. 4.21 Methyl esterdimeracid gm... 37.00 Zinc stearate per cent 05 These materials weremixed and heated for 58 hours at 192 C. and the resulting polyester hada molecular weight of about 5100. It was soluble and stable in Base OilA, a paraflinic lube oil having a viscosity of about 43 seconds Sayboltat 210 F. and a V. I. of about 112-114 and when dissolved therein showedthe following viscosity characteristics.

P t F. 210 F.

ercen Polymer I 0. s. s. s. U. o. s. s. s. U.

a 50. e 234. 2 1. 57 50. 93 e 67.0 309.6 10.26 60. 13 133 Example 9Iso-octyl succinic acid gm. 36

Octadeconediol gm. 12 Zinc stearate catalyst per cent 0.5

These materials were heated at 192 C. for 92 hours, and the resultingpolyester had a molecular weight of 3900. It was insoluble in Base Oil Abut soluble in a naphthenic base lube oil, and when dissolved thereinshowed the following viscosity characteristics:

These materials were heated for 92 hours at 192 C., and the resultingpolyester had a molecular weight of 3800. It was soluble and stable inBase Oil A, and when dissolved therein showed the following viscositycharacteristics:

P t 100 F. 210 F.

ercen Polymer I G. S S. S. U. C. S. S. S. U.

Example 11 hours. The solution was thick and clear and ,stable.Decamethylene glycol gm. 11.23 Niethyl ester dimer acid gm. 36.99viscosity Characteristics Zinc stearate per cent-.. 0.5 5 Naphthenicbase lube 011 6 6 (s. A. E. 20) "gm.-- 100 v.1.

These materials were heated at 192 C. for 30 hours, and at the end ofthe period the blend 10 0i! Dasestock 66.2 305.9 6.72 48.14 38.2 wasthick and clear. Concentrate (30% Poly V. I. of resulting concentrate.mer) 639 2992 31.2 147.2 50.0

v15. at 100 F. v15. at 210 F, Diluted with more of same oil:

. o. s. s. s. U. o.s. s. s. U. 0 Vis. at 100 F. Vis. at 210 F. v PercentV I Polymer 94.19.20 95.3 440.1 7.71 51.53 17.5 0.5, 5, 5,11, 0, s, s,s,Blend (30% polymer) 502 2,319 35.9 168.0 102.5

6 163.3 754.5 15.35 79.11 102.9 3 99.7 460.7 10.40 60.62 03.4 Afterdiluted with more of same naphthenic mineral oil: It is not intendedthat this invention be limited to the specific examples which have beenat 5 at given merely for the sake of illustration but only Percent bythe appended claim 1n which it is intended Pmym" S SU' 5.51;. to claimall novelty inherent in the invention as well as all modificationscoming within the 9&5 45 8,02 51 43 28,0 scope and spirit of theinvention. 3 111.8 516.5 9.10 66.13 43 What is claimed is; 6 199's 923'164 The process which comprises reacting a substantially pure methyldilinoleate with deca- The concentrate Was ble d in Base Oil A methyleneglycol in the presence of about 0.3 to and found to be soluble andstable, and showed 1,0% of zinc dilinoleate having a molecular the folow viscosity characteristics! 3 weight of about 1,000, at a temperatureof about 180 C. to 220 C. for a suflicient reaction time o o to producea high molecular weight polyester. V.t100 F. v.1;210 F. 2 154115 a 8 VJ,DAVID W. YOUNG. oymer es s. s. U. as s. s. U. JULIUS ROCCA' 49REFERENCES CITED 8.0 214.2 11.15 03.39 140 2.5 24.7 207.0 7.77 51.50139.5 g ifig gg i fg are of record in the UNITED STATES PATENTS Example12 Number Name Date Polyvmyl 10 2,342,113 Blair Feb. 22, 1944 Methyl ese of dlmer 291d 40 2,360,393 Burrell Oct. 17, 1944 Zinc stearate "percent 0.5 2,360,394 Burrell Oct. 17, 1944 Heavier naphthenic oil2,373,015 Cowan et a1. Apr. 3, 1945 (50 sec. vis/2l0 F.) gm glairh IAIay1945 es These materials were heated at 192 0. for 82 2,416,433 f f 5 25,3:?

2,429,219 Cowan et a1 Oct. 21, 1947

